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T'ai chi for the treatment of 
osteoarthritis: a systematic review and 
meta-analysis 



Jung Won Kang, 1 Myeong Soo Lee, 2 ' 3 Paul Posadzki, 3 Edzard Ernst 2 



To cite: Kang JW, Lee MS, 
Posadzki P, et al. T'ai chi for 
the treatment of 
osteoarthritis: a systematic 
review and meta-analysis. 
BMJ Open 2011 ;1:e000035. 
doi:10.1136/bmjopen-2010- 
000035 

► Prepublication history for 
this paper is available online. 
To view these files please 
visit the journal online (http:// 
bmjopen.bmj.com). 



Received 15 December 2010 
Accepted 17 February 2011 



This final article is available 
for use under the terms of 
the Creative Commons 
Attribution Non-Commercial 
2.0 Licence; see 
http://bmjopen.bmj.com 



department of Acupuncture 
& Moxibustion, College of 
Korean Medicine, Kyung Hee 
University, Seoul, Republic of 
Korea 

2 Brain Disease Research 
Centre, Korea Institute of 
Oriental Medicine, Daejeon, 
South Korea 

Complementary Medicine, 
Peninsula Medical School, 
University of Exeter, Exeter, 
UK 



ABSTRACT 

Objectives: To summarise and critically evaluate the 
evidence from randomised clinical trials (RCTs) of t'ai 
chi as a treatment for patients with osteoarthritis (OA). 
Design: Eleven databases were searched from their 
inception to July 2010. RCTs testing t'ai chi against 
any type of controls in human patients with OA 
localised in any joints that assessed any type of clinical 
outcome measures were considered. Two reviewers 
independently performed the selection of the studies, 
data abstraction and validations. The risk of bias was 
assessed using Cochrane criteria. 
Results: Nine RCTs met the inclusion criteria, and 
most of them had significant methodological 
weaknesses. Six RCTs tested the effects of t'ai chi 
compared with that of an attention-control 
programme, a waiting list and routine care or self-help 
programmes in patients with OA in the knee. The 
meta-analysis suggested that t'ai chi has favourable 
effects on pain (n=256; standard mean difference 
(SMD), -0.79; 95% CI -1.19 to -0.39; p=0.0001; 
l 2 =55%), physical function (n=256; SMD, -0.86; 
95% CI -1.20 to -0.52; p<0.00001; l 2 =38%) and 
joint stiffness (n=256; SMD, -0.53; 95% CI -0.99 to 
-0.08; p=0.02; l 2 =67%). 

Conclusion: The results are encouraging and suggest 
that t'ai chi may be effective in controlling pain and 
improving physical function in patients with OA in the 
knee. However, owing to the small number of RCTs 
with a low risk of bias, the evidence that t'ai chi is 
effective in patients with OA is limited. 



Correspondence to 

Dr Myeong Soo Lee; 
drmslee@gmail.com 



INTRODUCTION 

Osteoarthritis (OA) is the most common 
degenerative joint disease and affects the 
knees, hips, hands and spine. It is charac- 
terised by degradation of the joints, 
including cartilage surfaces and subchondral 
bone, causing joint-space narrowing, pain, 
stiffness, swelling, tenderness and reduced 
physical function. 1 2 Approximately 5% and 
10% of adults aged 60 years or older suffer 
from OA of the hip 1 and knee, 2 respectively. 
Because there is no known cure for OA, the 
main therapeutic strategy is symptomatic. 
Treatment includes analgesics, non-steroidal 



ARTICLE SUMMARY 



Article focus 

■ T'ai chi is a form of physical exercise that may 
offer physiological and psychological benefits to 
osteoarthritis sufferers. 

Key messages 

■ This systematic review offers limited evidence 
suggesting that t'ai chi may be effective for 
controlling pain and improving physical function 
in patients with osteoarthritis in the knee. 

Strengths and limitations of this study 

■ The strength of this systematic review is its 
extensive, unbiased search of various databases 
without language restriction. 

■ Our systematic review pertains to the potential 
incompleteness of the evidence reviewed, 
including publication and location bias, poor 
quality of the primary data and poor reporting of 
results. 



anti-inflammatory drugs, COX-2 inhibitors, 
glucocorticoids, topical analgesics and carti- 
lage protective agents (eg, diacerein, glucos- 
amine and chondroitin). Exercise is often 
recommended for managing OA, and 
there is some evidence of its effectiveness. 2 6 7 
However, total hip or knee replacements may 
often be the most effective treatments. 1 2 

T'ai chi is a form of complementary 
therapy with similarities to aerobic exercise 
that involves relaxation, deep breathing 
techniques and slow movements. 8 There are 
two systematic reviews of t'ai chi for OA 9 
or musculoskeletal pain. 10 One of them 
included five randomised clinical trials 
(RCTs) and seven controlled clinical trials 
compared with several types of controls. This 
review suggested that TC may be beneficial 
for pain control in patients with knee OA, 
although the review is outdated. 9 Recently, 
another review was published in 2009 that 
was based on the same four RCTs for OA 
as well as one RCT for arthritis, one RCT 
for tension headache and one RCT for 



Kang JW, Lee MS, Posadzki P, era/. BMJ Open 201 1 ;1 :e000035. doi:1 0.1 136/bmjopen-201 0-000035 



1 



T'ai chi for the treatment of osteoarthritis 



rheumatoid arthritis. This review also showed some 
favourable effects of t'ai chi for musculoskeletal pain, 
although the authors pooled the trials regardless of 
clinical heterogeneity, and the review is also now 
outdated. 

Therefore, the aim of this article was to update, 
complete and critically evaluate the evidence from RCTs 
of t'ai chi as a method of treatment for patients with OA 
of any joint. 

METHODS 
Searching 

Electronic databases were explored from their respective 
inceptions to July 2010; MEDLINE, AMED, EMBASE, 
CINAHL, five Korean Medical Databases (Korean 
Studies Information, DBPIA, Korea Institute of Science 
and Technology Information, KoreaMed, and Research 
Information Service System), Chinese Medical Databases 
(China National Knowledge Infrastructure: CNKI) and 
the Cochrane Library. The search strategies are shown in 
supplement 1. In addition, our own departmental files 
were manually searched. The references of all located 
articles and the proceedings of the First International 
Conference of T'ai chi for Health (December 2006, 
Seoul, South Korea) were also hand-searched for further 
relevant articles. No restrictions on years or publication 
status were imposed. We did not publish the protocol in 
advance. 

Selection 

All prospective RCTs of t'ai chi for OA were included 
without restrictions based on joint location (eg, chronic 
pain of the knee, hip or back). Trials comparing t'ai chi 
with any type of control intervention were also included, 
as were dissertations and abstracts. Any trials with t'ai chi 
as part of a complex intervention were excluded. 

Data abstraction and study characteristics 

Hard copies of all articles were obtained and read in full 
by two independent reviewers (MSL andJWK). The data 
from these articles were validated and abstracted 
according to predefined criteria that included the 
author information, the country of origin of the study, 
the sample size, the age of the participants, the site and 
duration of OA, the regimen of the experimental and 
control interventions, the main outcome, the associated 
adverse events and the author's conclusion (table 1). 

Validity assessment 

The risk of bias was assessed using the Cochrane classi- 
fication with four criteria: sequence generation, alloca- 
tion concealment, blinding and incomplete outcome 
measurement. ' A low risk of bias for assessor blinding 
was assumed if specified in the text regardless of the type 
of outcome measures (even for self-reported outcome 
measures). We assumed that the assessor was the person 
in charge of managing the outcome measures. 
Disagreements were resolved by discussions between the 
reviewers (MSL and JWK). 



Quantitative data synthesis 

Because there was no important clinical heterogeneity, 
we synthesised the results in a meta-analysis. The mean 
change in outcome measures between the end of the 
final intervention (post-treatment) and the baseline was 
used to assess the differences between intervention and 
control groups. Standardised mean differences (SMDs) 
were used because the studies measured the outcomes 
on different scales (WOMAC and VAS). SMDs and 95% 
CIs were calculated using Cochrane Collaboration soft- 
ware (Review Manager Version 5.0 for Windows; 
Copenhagen: The Nordic Cochrane Centre). For studies 
with insufficient information, we contacted the primary 
authors to acquire and verify data when possible. For one 
trial, 13 we contacted the authors to check the SDs of the 
original raw data because they reported the same SDs for 
the t'ai chi and control groups. The original authors 
clarified that the reported values did not differ from the 
raw data. Summary estimates of the treatment effect 
were calculated using the random effects model to 
account for expected heterogeneity. Differences 
between the treatment groups and the control groups 
were considered relevant in the context of this study. For 
one trial, 12 the author did not report the SD of changes 
for any outcomes. We therefore used the pre- and post- 
treatment means and the SDs for each group, and 
assumed a conservative within-subject pre-test— post-test 
correlation of 0.5 21 to calculate the SDs of change in 
each group using the methods in the Cochrane Handbook 
for Systematic Reviews of Interventions' 2 ^ Cochrane 's Q test 
and I 2 were used to assess statistical heterogeneity. We 
determined that there was considerable heterogeneity 
when Cochrane's Q test result was determined with 
p<0.10, and I 2 was above 75%. If a sufficient number of 
studies (at least 10 studies) were available, we attempted 
to assess publication bias using a funnel plot or Egger's 
regression test, whereby effect estimates of the common 
outcome measures were plotted against the sample 

23 24 

size. 

RESULTS 

Trial flow and study characteristics 

The literature search revealed 117 articles, of which 108 
studies were excluded. The reasons for article exclusion 
during the selection process are described in figure 1. 
Key data regarding the nine included RCTs are 
summarised in table 1. 11-19 A total of 521 participants 
were included in these trials. Four RCTs originated in 
the USA, 12 13 18 19 three RCTs were from Korea, one 
RCT was from China, 11 and one RCT was from 
Australia. 17 Six RCTs included patients with knee 
OA, 11-16 while the other three RCTs included patients 
with hip, knee or multiplejoint OA. 1719 Yang-style 
t'ai chi was used in four trials, 11-13 18 Sun-style was used 
in three trials, 15 17 Wu-style was used in one trial, 19 and 
one trial did not report the style of t'ai chi used. 14 All 
RCTs had a parallel-group design. 

Most trials had a relatively small sample size, and 
only five trials were based on a sample size 



2 



Kang JW, Lee MS, Posadzki P, et al. BMJ Open 201 1 ;1:e000035. doi:1 0.1 1 36/bmjopen-201 0-000035 



T'ai chi for the treatment of osteoarthritis 




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Kang JW, Lee MS, Posadzki P, etal. BMJ Open 201 1 ;1 :e000035. doi:1 0.1 136/bmjopen-201 0-000035 



T'ai chi for the treatment of osteoarthritis 



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Papers identified (n=117) 










Excluded after scanning titles / abstract (n=73) 

• Not relevant to tai chi (n=27) 

■ Not concerned with OA (n=25) 

• Not clinical trial (n=2 1 ) 







Papers retrieved for further evaluation 
(n=44) 



Exeluded after full assessment (n=35): 

■ Uncontrolled observational studies (n=l 1) 
•NonRCTs(n=18) 

• Case study (n=l) 

■ Duplicate publication in conference 

proceeding (n=2) 

■ RCT excluded because (n=3) 

- not concerned with OA only (n=l) 

- duplicate publication with difference 

main outcome measures (n=l) 

- duplicate publication in conference 
proceeding (n=l) 



Included RCTs (n=9) 



Included in meta-analysis (n=6) 



Figure 1 Flow chart of the trial selection process. OA, 
osteoarthritis; RCT, randomised clinical trial. 



calculation. 12 13 15 ~ 17 All of the included trials employed 
appropriate sequence generation methods for random- 
isation (table 2). The authors reported that they 
employed assessor blinding in five RCTs, 1 1-14 17 while 
blinding was unclear in the other four RCTs. 15 16 18 19 
Five RCTs adopted an allocation concealment 
method, 11 13-15 19 two RCTs 12 17 failed to do so, and this 
parameter was unclear in two RCTs. 16 18 The risk of bias 
for reporting participant dropout or withdrawal was low 
in all RCTs. Four RCTs had an intention-to-treat anal- 



ysis. 



13 14 17 19 



Two trials had a low risk of bias in the 



selective outcome reporting, 13 17 and the other two 
studies were at high risk of bias. 15 18 

Quantitative data synthesis 

Effects of t'ai chi on patients with knee OA 

Six RCTs tested the effects of t'ai chi compared with 
attention control, 11 13 a waiting list, 14 routine care 15 or 
self-help programmes 16 in patients with knee OA. The 
meta-analysis showed favourable effects of t'ai chi on 
pain (n=256; SMD, -0.79; 95% CI -1.19 to -0.39; 
p=0.0001; heterogeneity: X 2 =H-13, p=0.05, I 2 =55%; 
figure 2A), physical function (n=256; SMD, -0.86; 95% 
CI -1.20 to -0.52; p<0.00001; heterogeneity: X 2 =8.08, 
p=0.15, I 2 =38%; figure 2B) and joint stiffness (n=256; 



4 



Kang JW, Lee MS, Posadzki P, era/. BMJ Open 201 1 ;1:e000035. doi:1 0.1 1 36/bmjopen-201 0-000035 



T'ai chi for the treatment of osteoarthritis 



Table 2 Risk of bias of included randomised controlled trials* 





Random 








Reporting 


Intention- 


Selective 


Study: first author 


sequence 


Allocation 


Patient 


Assessor 


drop-out or 


to-treat 


outcome 


(year) 


generation 


concealment 


blinding 


blinding 


withdrawal! 


analysis! 


reporting 


Nl (2010) 


L 


L 


i i 
H 


L 


1 

L 


i i 
H 


1 1 

u 


tJrisrnee (2007) 


L 


1 1 
H 


i i 

H 


1 

L 


i 

L 


i i 

H 


1 1 


vvdiiy ^uuy^ 


1 

L 


1 


u 
n 


1 


1 


1 

L 




Lee (2009) 14 


L 


L 


H 


L 


L 


L 




Song (2003) 15 


L 


L 


H 


U 


L 


H 


! 


Song (2009) 16 


L 


U 


H 


U 


L 


H 




Fransen (2007) 17 


L 


H 


H 


L 


L 


L 




Hartman (2000) 18 


L 


U 


H 


U 


L 


H 


H 


Adler (2007) 19 


L 


L 


H 


U 


L 


L 


U 



'Domains of quality assessment based on Cochrane tools for assessing risk of bias. 
t/Two domains referring to 'incomplete outcome data' in the Cochrane tools for assessing risk of bias 
H, high risk of bias; L, low risk of bias; U, unclear (uncertain risk of bias). 




SMD, 



-0.53; 95% CI 

,2 



-0.99 to -0.08; p=0.02; hetero- 
geneity: X'= 15 -28, p=0.009, I 2 =67%; figure 2C). A 
subanalysis was performed to explore whether hetero- 
geneity could be partially explained by the type of 
control intervention. 

T'ai chi versus attention control 

Three RCTs 11-13 compared the effects of t'ai chi on 
pain, physical function and joint stiffness with attention 
control in patients with knee OA. All trials reported 
favourable effects of t'ai chi on pain reduction. The 
meta-analysis also showed superior effects of t'ai chi for 
pain reduction compared with attention control 
(n=100; SMD, -1.18; 95% CI -1.82 to -0.54; p=0.0003; 
heterogeneity: X 2 =4.28, p=0.12, I 2 =53%; figure 2A). 

Two 11 13 out of three RCTs 11-13 showed favourable effects. 
The meta-analysis showed the favourable effects of t'ai chi 
on physical function compared with attention control 
(n=100; SMD, -1.20; 95% CI -1.74 to -0.67; p<0.0001; 
heterogeneity: X 2 =2-99, p=0.22, 1 2 =33%; figure 2B). 

Three RCTs assessed the effects of t'ai chi on 
joint stiffness compared with attention control, 11 3 
only one of the three trials reported favourable effects 
The meta-analysis did not show any positive effects of 
t'ai chi (n=100; SMD, -0.82; 95% CI -1.67 to 0.04; 
p=0.06; heterogeneity: X 2 =8M, p=0.02, I 2 =75%; 
figure 2C) . 

One RCT compared the effect of t'ai chi on the quality 
of life compared with attention control, but it failed to 
show any favourable effect on this condition. 13 

T'ai chi versus routine treatments, a waiting list or a self-help 
programme 

Three RCTs assessed the effectiveness of t'ai chi on pain 
caused by knee OA compared with routine treatments, 
a waiting list or a self-help programme. 14 16 Two RCTs 
suggested a significant pain reduction compared with 
the waiting control 14 and the routine treatments, 15 while 
the other RCT did not. 16 The meta-analysis showed 
favourable effects of t'ai chi on pain reduction 
(n=156; SMD, -0.47; 95% CI -0.79 to -0.14; p=0.005; 
heterogeneity: X 2 =0.96, p=0.62, I 2 =0%; figure 2A). 



but 

n 



Three RCTs tested the effect of t'ai chi on physical 
function compared with routine treatments, awaiting list 
or a self-help programme. 14 15 Two RCTs showed 
significantly favourable effects, 15 16 while the other trial 
did not. 14 The meta-analysis showed superior effects of 
t'ai chi on physical function compared with routine cares 
(n=156; SMD, -0.60; 95% CI -0.93 to -0.28; p=0.0003; 
heterogeneity: X 2 =0.79, P=0.67, I 2 =0%; figure 2B). 

Three RCTs assessed the effects of t'ai chi on joint 
stiffness compared with routine treatments, a waiting list 
or a self-help programme. 14 16 One RCT showed signif- 
icantly favourable effects of t'ai chi, 15 while two trials did 
not. 14 16 The meta-analysis did not show any significant 
effects of t'ai chi on joint stiffness (n=156; SMD, —0.30; 
95% CI -0.79 to 0.19; p=0.23; heterogeneity: X 2=4 - 3 9. 
p=0.11, I 2 =54%; figure 2C). 

Effects of t'ai chi in patients with multiple-joint OA 

Three RCTs tested the effects of t'ai chi compared with 
hydrotherapy, a waiting list, routine treatments or 
participation in bingo games in patients with multiple 
joint OA. 17 19 One RCT with three parallel groups failed 
to show any superior effects of t'ai chi on pain reduction, 
physical function and quality of life when compared with 
hydrotherapy or a waiting-list control group but did show 
improved physical function when compared with the 

17 

waiting-list control group. The second RCT showed 
favourable effects of t'ai chi on the quality of life, 
compared with routine treatments, but not on pain 
reduction. 18 The third RCT did not show any significant 
differences in pain reduction, physical function or joint 
stiffness between t'ai chi and participation in bingo 

19 

games. 



Adverse effects 

Four RCTs 1 1-13 17 

other five RCTs 14-1 " 1B la did not. None of the four RCTs 
reported any serious adverse effects. Two RCTs reported 
minor muscle soreness and foot and knee pain in the 
early days of intervention. 11 12 One RCT reported 
increased knee pain and two cancer occurrences that 



assessed adverse effects, while the 

14-16 18 19 



Kang JW, Lee MS, Posadzki P, era/. BMJ Open 201 1 ;1 :e000035. doi:1 0.1 136/bmjopen-201 0-000035 



5 



T'ai chi for the treatment of osteoarthritis 



Figure 2 Forest plot of the 
effects of t'ai chi (TC) on (A) pain, 
(B) physical function and (C) joint 
stiffness in patients with knee 
osteoarthritis 



(A) Pain 



Tai chi 



Std. Mean Difference 



Study or Subgroup Mean SD Total Mean SD Total Weight IV. Random. 95% CI 



1.1.1 TC vs. attention control 

Brismee2007 -2.26 2.37 18 -0.79 1.79 13 

Ni 2010 -1.36 0.22 14 0.07 1 15 

Wang 2009 -157.25 104.6 20 -38.45 104.6 20 

Subtotal (95% CI) 52 48 

Heterogeneity: Tau 2 = 0.17; Chi 2 = 4.28, df = 2 {P = 0.12); I 2 = 53% 
Test for overall effect: Z = 3.59 (P = 0.0003) 

1.1.2 TC vs. routine cares 

15 
21 
39 
75 



Total (95% CI) 133 123 

Heterogeneity: Tau 2 = 0.13; Chi 2 = 11.13, df = 5 (P = 0.05); I 2 = 55% 
Test for overall effect: Z = 3.89 (P = 0.0001 ) 



Lee 2009 


-2 2 


4.1 


29 


-0.2 1.8 


Song 2003 


-2.45 


3.9 


22 


0.61 5.1 


Song 2009 


-1.36 


3.38 


30 


-0.48 2.53 


Subtotal (95% CI) 






81 




Heterogeneity: Tau 2 = 0 


00; Chi 2 = 


0.96, df 


= 2(P 


= 0.62); l 2 = 


Test for overall effect: Z 


= 2.82 (P 


= 0.005) 







15.1% 
12.0% 
16.5% 
43.6% 



17.3% 
17.8% 
21.4% 
56.4% 



-0.67 [-1.40, 0.07] 
-1.89 [-2.78, -0.99] 
-1.11 [-1.78, -0.44] 
-1.18 [-1.82, -0.54] 



-0.56 [-1.20, 0.07] 
-0.66 [-1.28, -0.05] 

-0.30 [-0.78, 0.18] 
-0.47 [-0.79, -0.14] 



-0.79 [-1.19, -0.39] 



Std. Mean Difference 
IV. Random. 95% CI 



-4 -2 0 2 4 
Favours tai chi Favours control 



(B) Physical function 



Study or Subgroup 



Tai chi 
Mean SD Total 



Control Std. Mean Difference 

Mean SD Total Weight IV. Random. 95% CI 



Std. Mean Difference 
IV. Random. 95% CI 



1.2.1 TC vs. attention control 

Brismee 2007 -10.92 13.14 18 0.14 10.93 13 14.0% 

Ni 2010 -6.17 1.96 14 -1.72 2.63 15 11.0% 

Wang 2009 -506.75 305.5 20 -182.15 305.5 20 16.5% 

Subtotal (95% CI) 52 48 41.5% 
Heterogeneity: Tau 2 = 0.08; Chi 2 = 2.99, df = 2 (P = 0.22); I 2 = 33% 
Test for overall effect: Z = 4.39 (P < 0.0001 ) 

1.2.2 TC vs. routine cares 

Lee 2009 -9.4 14.4 29 -2.7 10.8 15 17.5% 

Song2003 -11.09 12 22 -1.33 10.6 21 17.7% 

Song 2009 -0.76 14.77 30 6.19 11.69 39 23.3% 

Subtotal (95% CI) 81 75 58.5% 
Heterogeneity: Tau 2 = 0.00; Chi 2 = 0.79, df = 2 (P = 0.67); I 2 = 0% 
Test for overall effect: Z = 3.61 (P = 0.0003) 

Total (95% CI) 133 123 100.0% 

Heterogeneity: Tau 2 = 0.07; Chi 2 = 8.08, df = 5 (P = 0.15); I 2 = 38% 
Test for overall effect: Z = 4.93 (P < 0.00001) 



-0.88 [-1.63, -0.13] 
-1.86 [-2.75,-0.96] 
-1.04[-1.71,-0.38] 
-1.20 [-1.74, -0.67] 



-0.49 [-1.13, 0.14] 
-0.84 [-1 .47, -0.22] 
-0.52 [-1.01, -0.04] 
-0.60 [-0.93, -0.28] 



-0.86 [-1.20, -0.52] 



-4 -2 0 2 4 

Favours tai chi Favours control 



(C) Stiffness 



Tai chi 



Control 



Std. Mean Difference 



Study or Subgroup Mean SD Total Mean SD Total Weight IV. Random. 95% CI 

1.3.1 TC vs. attention control 

-1.83 [-2.72, -0.94] 
-0.46 [-1.09, 0.17] 
-0.29 [-1.01, 0.43] 
-0.82 [-1.67, 0.04] 



Ni 2010 -0.66 0.25 14 -0.05 0.38 15 13.0% 

Wang 2009 -73.05 48.62 20 -50.15 48.62 20 17.1% 

Brismee2007 -0.87 1.47 18 -0.44 1.39 13 15.6% 

Subtotal (95% CI) 52 48 45.7% 
Heterogeneity: Tau 2 = 0.43; Chi 2 = 8.03, df = 2 (P = 0.02); I 2 = 75% 
Test for overall effect: Z = 1 .87 (P = 0.06) 



Std. Mean Difference 
IV. Random. 95% CI 



1.3.2 TC vs. routine cares 



Song 2003 


-0.91 


1.6 22 0.23 1.8 


21 


17.4% 


-0.66 [-1.27, 


-0.04] 


Lee 2009 


-1.2 


2.1 29 -0.3 1.4 


15 


17.1% 


-0.47 [-1.10 


0.17] 


Song 2009 


0.46 


1.4 30 0.25 2.07 


39 


19.9% 


0.11 [-0.36 


0.59] 


Subtotal (95% CI) 




81 


75 


54.3% 


-0.30 [-0.79 


0.19] 


Heterogeneity: Tau 2 = 


0.10; Chi 2 = 


4.39, df=2(P = 0.11); I 2 = 


54% 








Test for overall effect: 


Z= 1.21 (P 


= 0.23) 










Total (95% CI) 




133 


123 


100.0% 


-0.53 [-0.99, 


-0.08] 


Heterogeneity: Tau 2 = 


0.22; Chi 2 = 


15.28, df = 5 (P = 0.009); I 


= 67% 








Test for overall effect: 


Z = 2.28 (P 


= 0.02) 











-4 -2 0 2 4 
Favours tai chi Favours control 



were not related to the interventions. 13 The other RCT 
reported serious adverse effects that were not related to 
the intervention. 17 

DISCUSSION 

Overall, this systematic review suggests that t'ai chi may 
be an effective treatment for pain and physical function 
associated with knee OA, compared with attention 
control or routine care. However, several caveats must be 
considered. For joint stiffness, the evidence was not 



robust, and for a mixed population with hip or knee OA, 
the evidence is not sufficient to conclude whether t'ai 
chi was beneficial. 

Our review aimed to update and complete the 
evidence by adding recent RCTs of t'ai chi as a method 
of treatment in patients with OA. Compared with two 
previous reviews, 9 10 we identified four new RCTs with 
a low risk of bias 11 1 15 and successfully updated the 
evidence for therapy. The results of our review are 
similar to the other two reviews. 10 14 One previous 



6 



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T'ai chi for the treatment of osteoarthritis 



review showed that t'ai chi may be beneficial for pain 
control in patients with knee OA, while the other 
review 10 also reported some favourable effects of t'ai chi 
for musculoskeletal pain. However, both reviews 
expressed concern regarding the poor methodological 
quality of the included primary studies. 

Previous systematic reviews have suggested that there 
are clinically important differences among various ther- 
apies, compared with various control groups, in OA pain 
reduction and functional improvement. 2 The effect size 
of the pain reduction and the functional improvement 
in our review was higher than exercise, non-steroidal 
anti-inflammatory drugs and drug therapy; this effect is 
clinically significant. 2 However, these results are difficult 
to compare quantitatively owing to the use of different 
assessment measures for evaluating pain and the use of 
different controls for evaluating the comparisons. 

Limitations of this study include the potential incom- 
pleteness of the evidence reviewed. The distorting effects 
of publication and location bias on systematic reviews 
and meta-analyses are well documented. 25 27 We are 
confident that our search strategy located all relevant 
data; however, some degree of uncertainty remains. 
Another possible source of bias is the fact that half of the 
included trials were performed in China and Korea, 
where apparently no negative studies have been 
reported. 28 Our review may be affected by the potentially 
poor quality of the primary data and poor reporting of 
results, which were highly heterogeneous in virtually 
every respect. 

The risk of bias in the studies was assessed based on 
the descriptions of sequence generation, allocation 
concealment, blinding, incomplete outcome measures 
and selective outcome reporting. Based on these assess- 
ments, the risk of bias varied across the included studies. 
Only three RCTs had a low risk of bias, 13 14 17 and two 
studies had a moderate risk of bias. 11 19 The other four 
RCTs were at high risk of being biased. 12 15 16 18 Five 
RCTs employed allocation concealment, 11 3 14 16 19 and 
four RCTs used an intention-to-treat analysis. 13 14 17 19 
Inappropriate allocation concealment and the lack of 
blinding exaggerate the results of outcome measures. 29 30 
Only two RCTs were at low risk of bias in selective 
outcome reporting. 13 17 Even though the authors 
reported that they employed assessor blinding, 11 14 17 
some outcomes that they measured relied on the 
patient's subjective reporting, and so the patient's and 
assessor's blinding becomes unachievable and irrelevant. 
The main limitations of the included studies were small 
sample sizes, the inadequate control for non-specific 
effects and a lack of power calculations or adequate 
follow-up. Additionally, the fact that t'ai chi interven- 
tions cannot control for placebo effects limits general- 
isability. Second, adequate follow-ups of 6—12 months 
are advisable for future studies of t'ai chi for OA. 

One could argue that the employment of the 
Cochrane risk-of-bias tool to assess the methodological 
bias in the clinical trial is not acceptable. This tool was 



recently recommended for assessing methodological 
quality in lieu of other scoring assessment tools, such as 
the Jadad scale. 20 It has been proposed that using 
a quality score for clinical trials is not adequate. 31 32 
Although the inter-rater disagreements across the 
domains were reported in the Cochrane risk-of-bias tool, 
their overall reliability was fair. 33 34 We also calculated 
our reliability for nine included trials with the Excel 
module (http://agreestat.com/agreestat.html). Our 
inter-rater agreement for the individual domains of the 
risk-of-bias tool to nine included trials ranged from 
substantial to almost perfect (0.88 for random sequence 
generation; 0.70 for allocation concealment; 1.00 for 
patient blinding; 0.85 for assessor blinding; 0.88 for 
reporting drop-out or withdrawal; 0.69 or intention-to- 
treat analysis; and 0.71 for selective outcome reporting). 
Therefore, the Cochrane risk-of-bias tool may be the 
most comprehensive tool with fair reliability that is 
currently available. 

Proponents of t'ai chi claim that it improves flexibility, 
strength and balance, especially in older people. Clearly, 
these claims need to be tested. The pooled results from 
six RCTs 11 16 suggested that pain intensity was reduced 
when patients used t'ai chi, compared with attention 
control or routine care for knee OA. However, three 
RCTs found that t'ai chi had no significant effect on 
pain reduction when compared with hydrotherapy, 
waiting list, routine treatments or participation in bingo 
games in multiple joint OA. 17 19 These results may be 
explained, in part, through inadequate blinding and 
control for non-specific effects in some of the positive 
studies, among other sources of bias. 

Assuming that t'ai chi was beneficial for treating OA, the 
possible mechanisms of action may be of interest. Regular 
t'ai chi has been postulated to improve balance and 
reduce the likelihood of falls by improving muscle flexi- 
bility and trunk rotation. T'ai chi is a form of physical 
exercise combined with relaxation. Physical movement in 
t'ai chi can improve joint stability and aid in reducing 
excess weight, effectively decreasing joint pain, increasing 
function and reducing the advancement of OA. 36 
Furthermore, t'ai chi may also influence the psychosocial 
quality of life, which may have a positive influence on 
chronic pain. 35 37 The question of whether t'ai chi is 
superior to other forms of therapeutic exercise is currently 
unanswered and is thus a topic for further investigation. 

Four of the reviewed studies reported minor adverse 
events related to t'ai chi. 11 " 13 17 T'ai chi appears to be 
generally safe, and serious adverse effects have not been 
reported. However, adverse effects were not the focus of 
this review and may require further research. 

Future RCTs of t'ai chi for OA should adhere to 
accepted standards of trial methodology. The studies 
included in this review show a number of problems that 
have been noted by other reviews of trials examining the 
efficacy of t'ai chi, such as the expertise of t'ai chi 
practitioners, the pluralism of t'ai chi, the frequency 
and duration of treatment, the use of validated primary 



Kang JW, Lee MS, Posadzki P, era/. BMJ Open 201 1 ;1 :e000035. doi:1 0.1 136/bmjopen-201 0-000035 



7 



T'ai chi for the treatment of osteoarthritis 



outcome measures and adequate statistical tests, and 
heterogeneous comparison groups. 38 39 Furthermore, 
even though it is difficult to blind subjects to treatment, 
employing assessor blinding and allocation concealment 
are important for reducing bias. A clinical study is only 
truly useful if the intervention used can be replicated; 
hence, the type of t'ai chi employed is important. There 
are significant differences between the numerous forms 
of t'ai chi, and a clear description of the t'ai chi inter- 
vention should be provided together with a description 
of the level of expertise of the instructors. 

In conclusion, there are encouraging results 
suggesting that t'ai chi may be effective in controlling 
pain and improving physical function in patients with 
knee OA. However, owing to the number of eligible 
RCTs and the often-poor quality of the available RCTs, 
the evidence is limited. 

Funding MSL was supported by Korea Institute of Oriental Medicine (K10251 
and K11111). 

Competing interests None. 

Contributors JWK and MSL designed the review, performed searches, 
appraised and selected trials, abstracted data, contacted authors for additional 
data, carried out the analysis and interpretation of the data, and drafted this 
report. PP and EE reviewed and critiqued the review protocol and this report, 
and assisted in designing the review. All authors read and approved the final 
version of the manuscript. 

Provenance and peer review Not commissioned; externally peer reviewed. 
Data sharing statement No additional data available. 



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